Solid-state image pickup apparatus, method of manufacturing the same, and image pickup apparatus

ABSTRACT

A solid-state image pickup apparatus includes a substrate, a wiring layer, and a waveguide. The substrate is provided with a pixel array portion constituted of a plurality of pixels each having a photoelectric converter that converts incident light into an electrical signal. The wiring layer includes a plurality of wirings and an insulating layer that covers the plurality of wirings that are laminated above the substrate. The waveguide guides light to each of the photoelectric converters of the plurality of pixels, the waveguide being formed in the wiring layer. The waveguide is formed to have a waveguide exit end from which light exits the waveguide so that a distance between the waveguide exit end and a surface of the photoelectric converter that receives light from the waveguide become shorter, as wavelengths of light guided by the waveguide are longer.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a divisional of U.S. patent application Ser.No. 12/660,728 filed Mar. 10, 2010, which claims priority from JapanesePatent Application No. JP 2009-058985 filed Mar. 12, 2009, all of whichare incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a solid-state image pickup apparatus, amethod of manufacturing the same, and an image pickup apparatus.

2. Description of the Related Art

In response to the progress of the increase in number of pixels and theminiaturization of a pixel size, there has been proposed a technique ofusing a waveguide structure as a means for increasing a light collectionefficiency of each pixel in a solid-state image sensor. In particular,in a CMOS image sensor, for forming a metal wiring on a light incidentside of a photodiode, a waveguide structure, which guides incident lightto a photodiode while confining the light and avoiding the metal wiring,is becoming a necessary technique.

A description will be given on an example of a solid-state image sensorhaving a waveguide structure in related art.

In a solid-state image sensor in related art, a photodiode thatfunctions as a photoelectric converter is formed in an area separated byan element-separation insulating film or the like formed on a siliconsubstrate. On an upper surface of the silicon substrate adjacent to thephotoelectric converter, a transfer gate electrode is disposed through agate insulating film formed of a silicon oxide film and the like.Further, on the upper surface of the silicon substrate, a plurality ofwiring layers made of a plurality of metal wirings are formed, and themetal wirings between the wiring layers are connected with each otherthrough a through hole (bear hole) as appropriate.

On an uppermost wiring layer, a color filter is provided through apassivation film and a planarization film. On the color filter, a microlens is disposed.

At a position corresponding to the micro lens and the photodiode, awaveguide that passes through the wiring layers is formed. The waveguideis formed by embedding a film having a little light-absorption property.

The waveguide optically connects an on-chip lens and a photodiode witheach other and has a function of efficiently guiding light incident onthe on-chip lens to the photodiode. Therefore, in the waveguide, amaterial having a refractive index higher than a material of aninsulating film that forms the wiring layers is filled (see, forexample, Japanese Patent Application Laid-open No. 2003-224249).

Along with the miniaturization, an absolute amount of incident light isreduced, and a light reception area of a photodiode that detects lightis also reduced. If the degrees of the reduction are the same for colors(RGB), a spectral balance of the colors is the same as that of aprevious generation, and a device design and a circuit design of aprevious generation only have to be improved to a small extent.

When incident light beams have the same light amount, in a case of, forexample, 1.75 μm□ cell and 1.1 μm□ cell, there are differences inquantum efficiency of the colors in the 1.1 μm□ cell along with theminiaturization. The light amounts of light (natural light) that entersthe on-chip lens are the same regardless of the colors. Therefore, iflight losses in components, such as the on-chip lens, the color filter,the planarization film, through which the incident light is guided areconstant, signals that are output from the colors are proportional tothe quantum efficiencies, with the result that the balance of the colors(spectral balance) may deteriorate.

There are some reports on a correction of the spectral balance.

The amounts of incident light are different between a pixel immediatelybelow a position where the on-chip lens is disposed and a pixeldistanced from the position. Therefore, a waveguide diameter of thedistanced pixel is set to be thick (see, for example, Japanese PatentApplication Laid-open No. 2006-190766).

In addition, in a system in which light is caused to be incident on aside of a photodiode of a solid-state image sensor, trenches are formedon a silicon substrate, depths of the trenches are set to be differentfor each color, and distances from bottom surfaces of the trenches tothe photodiode are changed (see, for example, Japanese PatentApplication Laid-open No. 2007-184603).

SUMMARY OF THE INVENTION

There is a problem of deterioration of the spectral balance along withthe miniaturization of a pixel.

In view of the above-mentioned circumstances, it is desirable to make itpossible to adjust the spectral balance to be constant in differences oflight dispersion angles from waveguide exit ends due to wavelengths oflight of the colors.

According to an embodiment of the present invention, there is provided asolid-state image pickup apparatus including a substrate, a wiringlayer, and the waveguide. The substrate is provided with a pixel arrayportion constituted of a plurality of pixels each having a photoelectricconverter. The photoelectric converter converts incident light into anelectrical signal. The wiring layer includes a plurality of wirings andan insulating layer that covers the plurality of wirings. The pluralityof wirings are laminated above the substrate. The waveguide guides lightto each of the photoelectric converters of the plurality of pixels. Thewaveguide is formed in the wiring layer. The waveguide is formed to havea waveguide exit end from which light exits the waveguide so that adistance between the waveguide exit end and a surface of thephotoelectric converter that receives light from the waveguide becomeshorter, as wavelengths of light guided by the waveguide are longer.

In the solid-state image pickup apparatus according to the embodiment ofthe present invention, the distance between the waveguide exit end fromwhich light exit the waveguide and the surface of the photoelectricconverter that receives light that exits the waveguide is set to beshorter, as the wavelength of light guided by the waveguide is longer.As a result, it is possible to adjust the spectral balance in thedifference of spread angles of light from the waveguide exit end due tothe wavelengths of the colors.

According to another embodiment of the present invention, there isprovided a method of manufacturing a solid-state image pickup apparatus.The method of manufacturing a solid-state image pickup apparatusincludes forming, on a substrate, a pixel array portion constituted of aplurality of pixels each having a photoelectric converter that convertsincident light to an electrical signal, forming, above the substrate, awiring layer including multilayer wirings and an insulating layer thatcovers the wirings, and forming, in the wiring layer, a waveguide thatguides light to the photoelectric converter of each of the plurality ofpixels. The waveguide is formed to have a waveguide exit end from whichlight exits the waveguide so that a distance between the waveguide exitend and a surface of the photoelectric converter that receives lightfrom the waveguide become shorter, as wavelengths of light guided by thewaveguide are longer.

In the method of manufacturing a solid-state image pickup apparatusaccording to the embodiment of the present invention, the distancebetween the waveguide exit end from which light exit the waveguide andthe surface of the photoelectric converter that receives light thatexits the waveguide is set to be shorter, as the wavelength of lightguided by the waveguide is longer. As a result, it is possible to adjustthe spectral balance in the difference of spread angles of light fromthe waveguide exit end due to the wavelengths of the colors.

According to another embodiment of the present invention, there isprovided an image pickup apparatus including a light-collecting opticalportion, a solid-state image pickup apparatus, and a signal processingportion. The light-collecting optical portion collects incident light.The solid-state image pickup apparatus receives light collected by thelight-collecting optical portion and perform photoelectric conversion.The signal processing portion processes a signal obtained by thephotoelectric conversion. The solid-state image pickup apparatusincludes a substrate provided with a pixel array portion constituted ofa plurality of pixels each having a photoelectric converter thatconverts incident light into an electrical signal, a wiring layerincluding a plurality of wirings and an insulating layer that covers theplurality of wirings that are laminated above the substrate, and awaveguide to guide light to each of the photoelectric converters of theplurality of pixels, the waveguide being formed in the wiring layer, thewaveguide being formed to have a waveguide exit end from which lightexits the waveguide so that a distance between the waveguide exit endand a surface of the photoelectric converter that receives light fromthe waveguide become shorter, as wavelengths of light guided by thewaveguide are longer.

In the image pickup apparatus according to the embodiment of the presentinvention, it is possible to adjust the spectral balance in thedifference of spread angles of light from the waveguide exit end due tothe wavelengths of the colors.

The solid-state image pickup apparatus of the present invention canadjust the spectral balance. Thus, an image synthesis margin can beobtained in making an adjustment for an image of a more natural color,and a color correction can be easily performed, with the result that theadvantage of obtaining an image excellent in color reproducingperformance can be provided.

By the method of manufacturing a solid-state image pickup apparatus ofthe present invention, the spectral balance can be adjusted. Thus, animage synthesis margin can be obtained in making an adjustment for animage of a more natural color, and a color correction can be easilyperformed, with the result that the advantage of obtaining an imageexcellent in color reproducing performance can be provided.

The image pickup apparatus of the present invention can adjust thespectral balance. Thus, an image synthesis margin can be obtained inmaking an adjustment for an image of a more natural color, and a colorcorrection can be easily performed, with the result that the advantageof obtaining an image excellent in color reproducing performance can beprovided.

These and other objects, features and advantages of the presentinvention will become more apparent in light of the following detaileddescription of best mode embodiments thereof, as illustrated in theaccompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic cross-sectional diagram showing a first example ofa structure of a solid-state image pickup apparatus;

FIG. 2 is an optical path diagram from a waveguide exit end to aphotoelectric converter;

FIG. 3 is a graph showing a relationship between an efficiency and adistance from the waveguide exit end to the photoelectric converter;

FIG. 4 is a graph showing a relationship between a reciprocal of theefficiency and the distance from the waveguide exit end to thephotoelectric converter;

FIGS. 5A to 5B are cross-sectional diagrams of a schematic structure forexplaining a first comparative example and a graph showing arelationship between the efficiency and a wavelength;

FIGS. 6A to 5B are optical path diagrams from a micro lens to an entryof the waveguide and a graph showing a relationship of the waveguideexit end to the photoelectric converter;

FIGS. 7A to 7B are cross-sectional diagrams of a schematic structure forexplaining a second comparative example and a graph showing arelationship between the efficiency and the wavelength;

FIG. 8 is a schematic cross-sectional diagram showing a second exampleof the structure of the solid-state image pickup apparatus;

FIGS. 9A to 9B are manufacture-process cross-sectional diagrams showinga first example of a method of manufacturing the solid-state imagepickup apparatus;

FIGS. 10A to 10C are manufacture-process cross-sectional diagramsshowing the first example of the method of manufacturing the solid-stateimage pickup apparatus;

FIGS. 11A to 11C are manufacture-process cross-sectional diagramsshowing the first example of the method of manufacturing the solid-stateimage pickup apparatus;

FIGS. 12A to 12B are manufacture-process cross-sectional diagramsshowing a second example of the method of manufacturing the solid-stateimage pickup apparatus;

FIGS. 13A to 13C are manufacture-process cross-sectional diagramsshowing the second example of the method of manufacturing thesolid-state image pickup apparatus;

FIGS. 14A to 14B are manufacture-process cross-sectional diagramsshowing a third example of the method of manufacturing the solid-stateimage pickup apparatus;

FIGS. 15A to 15C are manufacture-process cross-sectional diagramsshowing the third example of the method of manufacturing the solid-stateimage pickup apparatus; and

FIG. 16 is a block diagram showing an example of an image pickupapparatus according to a third embodiment of the present invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

Hereinafter, embodiments of the present invention will be described withreference to the drawings.

1. First Embodiment First Example of Structure of Solid-State ImagePickup Apparatus

A first example of a structure of a solid-state image pickup apparatusaccording to a first embodiment of the present invention will bedescribed with reference to a cross-sectional diagram of a schematicstructure of FIG. 1.

As shown in FIG. 1, on a substrate 11, a pixel array portion 13constituted of a plurality of pixels 12 each including a photoelectricconverter 21 is provided. The photoelectric converter 21 convertsincident light to an electrical signal. For the substrate 11, forexample, a silicon substrate as a semiconductor substrate is used. Thephotoelectric converter 21 is formed of a photodiode, for example.Further on the substrate 11, a transfer gate electrode 23 is formed tobe adjacent to the photoelectric converter 21 through a gate insulatingfilm 22.

Further, on the substrate 11, a protection film 41 that covers thephotoelectric converter 21, the transfer gate electrode 23, and the likeis formed. On the protection film 41, a planarization film 42 is formed.

Above the substrate 11, that is, on the planarization film 42, aplurality of wirings 32 are accumulated, and a wiring layer 31 includingan insulating layer 34 that covers the plurality of wirings 32 isformed.

Each of the wirings 32 is made of metal such as copper (Cu), tungsten(W), and aluminum (Al). Around the wiring 32, a barrier metal layer 33is formed, for example.

The insulating layer 34 is formed of, for example, a silicon oxide or alow dielectric constant material. For example, in a case where theinsulating layer 34 is made of the silicon oxide or asilicon-oxide-based material, the insulating layer 34 has a refractiveindex of 1.4 to 1.5.

In the wiring layer 31, waveguides 14 (14B, 14G, and 14R) are formed.The waveguides 14 guide light to the photoelectric converters 21 of theplurality of pixels 12. The waveguides 14 may partly be formed in theplanarization film 42. As an example, in FIG. 1, the waveguide 14R ispartly formed in the planarization film 42.

The waveguides 14 will be described in detail.

The waveguides 14 are each formed by filling a waveguide material 36into waveguide holes 35. The waveguide holes 35 are formed in the wiringlayer 31 so as to be separated from the wirings 32. For example, asshown in FIG. 1, the waveguide material 36 fills the waveguide holes 35,and is also formed on an upper portion of the insulating layer 34 of thewiring layer 31. Accordingly, the waveguide material 36 filled in thewaveguide holes 35 serves as the waveguides 14.

In addition, in the waveguides 14, distances L (Lb, Lg, and Lr) betweenwaveguide exit ends 14E from which light exits the waveguides 14 and thesurfaces of the photoelectric converters 21 that receive light exitedare set to be shorter, as wavelengths of light beams that are guided bythe waveguides 14 are longer. The waveguide exit ends 14E corresponds tothe bottom portions of the waveguide holes 35.

The waveguide material 36 that forms the waveguides 14 is formed of amaterial having a refractive index higher than that of the insulatinglayer 34, specifically, for example, a material having a hightransmittance of a wavelength in a visible light area. Examples of thematerial include a silicon nitride film, a diamond film, a compositematerial film of diamond and an organic-based material, a compositematerial film of titanium oxide and an organic-based material, and thelike.

The waveguides 14 are constituted of the first color (red) pixelwaveguide 14R, a second color (green) pixel waveguide 14G, and a thirdcolor (blue) waveguide 14B. The wavelengths of the first color (red),the second color (green), and the third color (blue) are shorter in thestated order. For example, a red color wavelength λr=650 nm, a greencolor wavelength λg=550 nm, and a blue color wavelength λb=450 nm areobtained. Those wavelengths are obtained at peak light intensities ofthe colors.

In addition, above each of the waveguides 14 (light incident side), acolor filter 51 is formed through a planarization film 44 that coversthe waveguide material 36. On the color filter 51, a micro lens 52 thatguides the incident light to a light entry of each of the waveguides 14is formed.

In this way, the micro lens 52 and the photoelectric converter 21 areoptically connected to each other through each of the waveguides 14.

Next, a description will be given on the distances L between thewaveguide exit ends 14E and the surfaces of the photoelectric converters21 that receive light exited from the waveguides 14.

A distance between the waveguide exit end 14E of the waveguide 14R fromwhich red light that has passed through a red color filter 51R exits andthe surface of the photoelectric converter 21 that receives light thathas exited the waveguide 14R is set as a distance Lr. Similarly, adistance between the waveguide exit end 14E of the waveguide 14G fromwhich green light that has passed through a green color filter 51G exitsand the surface of the photoelectric converter 21 that receives lightthat has exited the waveguide 14G is set as a distance Lg. A distancebetween the waveguide exit end 14E of the waveguide 14B from which bluelight that has passed through a blue color filter 51B exits and thesurface of the photoelectric converter 21 that receives light that hasexited the waveguide 14B is set as a distance Lb.

The distance Lr of the red pixel waveguide 14R is set to be shorter thanthe distance Lg of the green pixel waveguide 14G. Further, the distanceLg of the green pixel waveguide 14G is set to be shorter than thedistance Lb of the blue pixel waveguide 14B.

As an example, the size of each of the photoelectric converter 21 is setto 1.1 μm□, a diameter of the waveguide exit end 14E of the waveguide14B is set to 460 nm. In this case, for example, when the distanceLr=580 nm is set, Lg=690 nm, and Lb=840 nm are set.

It should be noted that in a case where the distances L (Lr, Lg, and Lb)are less than 300 nm, light that exits the waveguide exit ends 14E isalmost completely received by the photoelectric converters 21irrespective of the wavelengths of light that enters the waveguides 14.

Accordingly, in a case where the distance Lr<300 nm, the distance Lg<300nm, and the distance Lb<300 nm are satisfied, a relationship of Lr=Lg=Lbcan be set.

Of course, when the size of the photoelectric converter 21 is furtherreduced to be less than 1.1 μm□, it is necessary to reduce the distancesL.

Next, an example of determining the distance L will be described withreference to FIG. 2.

As shown in FIG. 2, light that exits the waveguide exit end 14E spreadsby diffraction and reaches the surface of the photoelectric converter21.

Here, a spread angle of the light that has exited the waveguide exit end14E is represented by 0, a radius of the waveguide 14 at the waveguideexit end 14E is represented by wf, and the distance from the waveguideexit end 14E of the waveguide 14 to the surface of the photoelectricconverter 21 is represented by L. Further, a wavelength of the incidentlight is represented by λ, and a radius of a spot formed on the surfaceof the photoelectric converter 21 is represented by W. The followingrelational expression can be obtained.

tan θ=W/L=λ/(πwf)  (1)

Therefore, the expression (1) can be transformed as follows.

wf=λL/πW  (2)

In the expression (2), the spot radius W is changed depending on thewavelengths λ and the distances L. This is because different diffractionstates are obtained depending on the difference in the wavelengths λ,and the shorter the wavelength λ becomes, the more the light that hasexited the waveguide exit end 14E spreads.

Here, from the expression (2), an efficiency that is a ratio of a spotdiameter (2 W) for each wavelength λ with respect to the distance L to alight reception area of the photoelectric converter 21 is calculatedwith a diameter (2 wf) of the waveguide exit end 14E of the waveguide 14being a parameter. FIG. 3 shows a result of the calculation. In thiscase, an area of the photoelectric converter 21 is set to 0.3 μm². Atthis time, the red color wavelength λr=650 nm, the green colorwavelength λg=550 nm, and the blue color wavelength λb=450 nm are set.

As shown in FIG. 3, in the case where the diameter 2 Wf of the waveguideexit end 14E is 460 nm or 700 nm, when the distance L is less than 300nm, the efficiency is 1. That is, light exited from the waveguide exitend 14E completely reaches the photoelectric converter 21.

Further, in the case of 2 wf=700 nm, the efficiency becomes constant(efficiency=1), when Lr=580 nm, Lg=690 nm, and Lb=840 nm are set.

As shown in FIG. 3, by determining the efficiency that is the ratio ofthe spot diameter (2 W) for each wavelength λ with respect to thedistance L to the light reception area of the photoelectric converter 21with the diameter (2 wf) of the waveguide exit end 14E being set as theparameter, the distance L for each color can be easily obtained.

In addition, in the case of the 1.1 μm□ cell shown in FIG. 3, areciprocal of the efficiency is obtained and corresponded to a verticalaxis, and the distance L from the waveguide exit end 14E to the surfaceof the photoelectric converter 21 is corresponded to a lateral axis in agraph shown in FIG. 4.

From a relationship between the reciprocal of the efficiency of thecolors and the distance L for each color shown in FIG. 4, in a casewhere the relationship among distances Lr, Lg, and Lb is approximated byusing a quadric equation with the reciprocal of the efficiency being setas a constant value, the following expression can be obtained as anapproximation.

8Lr ²=6Lg ²=4Lb ²  (3)

Accordingly, for example, when the distance Lr is set, the distances Lgand Lb can be determined. The same holds true for the distance Lg or Lb.

It should be noted that the distance L of each color obtained by usingthe expression (2) and the distance L of each color obtained by usingthe expression (3) may have an approximately 4% margin of error, but themargin of error is within the same margin of error in a manufacturingprocess of a semiconductor. Therefore, the margin of error is a matterof no importance.

In the above, the description is given on the case where the lightdispersed by the color filter 51 is the red, green, and blue light. Thedispersion by the color filter 51 is not limited to the above colors,and light dispersed may be complementary colors of the above colors. Inaddition, it is desirable to adjust the distance L from the waveguideexit end 14E of the waveguide 14 to the surface of the photoelectricconverter 21 for a wavelength of colors other than the red, green, andblue, such as orange and blue green.

(Modified Example of First Example of Structure of Solid-State ImagePickup Apparatus)

Further, in a case where the light incident positions of the waveguides14 are set on the same plane, and the surfaces of the photoelectricconverters 21 are positioned on the same surface of the substrate 11, itis possible to perform prescription based on the depths of thewaveguides 14. That is, a value obtained by subtracting the distance Lfrom a distance between the surface of the substrate 11 and a plane onwhich the light incident position of each waveguide 14 is disposedcorresponds to the depth of each waveguide 14. In this case, the depthof the red pixel waveguide 14R is the largest, and the depth of the bluepixel waveguide 14B is the smallest. The depth of the green pixelwaveguide 14G is smaller than that of the red pixel waveguide 14R andlarger than that of the blue pixel waveguide 14B.

For example, in a case where the thickness of the wiring layer 31 is2000 nm, the depths of the blue pixel waveguide 14B, the green pixelwaveguide 14G, and the red pixel waveguide 14R are approximately 1600 nmto 1800 nm, 1800 nm to 2000 nm, and 2000 nm to 2200 nm, respectively.But, the number of wiring layers of the wiring 32, the height of thewiring 32, the height of the insulating layer 34, and the like arelinked to a device speed, a power consumption, or the like, so the depthof the waveguide is selected in accordance with a performance of anapparatus.

(First Comparative Example of Solid-State Image Pickup Apparatus)

Next, a description will be given on a first comparative example withreference to FIG. 5.

As shown in FIG. 5A, in a solid-state image pickup apparatus 101 of afirst comparative example, a structure other than the waveguides 14 isthe same as that of the solid-state image pickup apparatus 1 describedabove with reference to FIG. 1. Therefore, only the waveguides 14 willbe described.

The waveguides 14 formed in the wiring layer 31 are the red pixelwaveguide 14R, the green pixel waveguide 14G, and the blue pixelwaveguide 14B. The distance L from the waveguide exit end 14E of each ofthe waveguides 14 to the surface of the photoelectric converter 21 isconstant.

For example, in the solid-state image pickup apparatus 101 of the firstcomparative example, the photoelectric converter 21 is formed to be 1.4μm□, and a diameter of each of the waveguide exit ends (bottom portions)14E of the waveguides 14 is formed to be 700 nm. The distances L areeach formed to be 580 nm.

In this case, as shown in FIG. 5B, an efficiency of the solid-stateimage pickup apparatus 101 is 40% to 45% in each of the red, green, andblue colors, and an approximately constant value is obtained.

Therefore, a difference of the efficiencies is not caused depending onthe colors. Further, a difference of the efficiencies due to thedistance L from the waveguide exit end 14E to the photoelectricconverter 21 is not caused in a case of L=580 nm. Thus, as describedabove, the distance L is set to 580 nm.

In addition, the efficiencies from the micro lens 52 to the waveguideexit end 14E are constant irrespective of the colors. For example, asshown in FIG. 6A, light that has exited the micro lens 52 is collectedand focused on an entry of the waveguide 14.

Here, an incident angle of light that is focused on the entry of thewaveguide 14 is represented by θ, a light-collecting spot radius at theentry of the waveguide 14 is represented by wf, and a distance from themicro lens 52 to the entry of the waveguide 14 is represented by f.Further, a wavelength of the incident light is represented by λ, and aradius of light that reaches the surface of the micro lens 52 isrepresented by W. An expression (4) of wf=λf/πW can be obtained as inthe expression (2) described above. In actuality, the radius W of theincident light corresponds to a radius of the micro lens 52.

Based on the expression (4), a calculation is executed in the case wherethe collected light spot diameter and the waveguide diameter are 700 nm.As a result, as shown in FIG. 6B, the efficiency from the micro lens 52to the waveguide exit end 14E becomes 1 or more in the cases of the red(R), green (G), and blue (B) light. Accordingly, the light collected tothe micro lens 52 is completely guided to the entry of the waveguide 14of the incident light irrespective of the colors of light.

(Second Comparative Example of Solid-State Image Pickup Apparatus)

On the other hand, as shown in FIG. 7A, in a solid-state image pickupapparatus 102 of a second comparative example, a structure other thanthe waveguides 14 is the same as that of the solid-state image pickupapparatus 1 described above with reference to FIG. 1. Therefore, onlythe waveguides 14 will be described.

The waveguides 14 formed in the wiring layer 31 are the red pixelwaveguide 14R, the green pixel waveguide 14G, and the blue pixelwaveguide 14B. The distances L from the waveguide exit ends 14E of thewaveguides 14 to the surfaces of the photoelectric converters 21 areconstant.

For example, in the solid-state image pickup apparatus 102 of the secondcomparative example, each of the photoelectric converters 21 is formedto be 1.1 μm□, and each of the diameters of the waveguide exit ends 14Eof the waveguides 14 is formed to be 460 nm. Each of the distances L isformed to be 580 nm.

In this case, as shown in FIG. 7B, the efficiencies of the solid-stateimage pickup apparatus 102 are about 40%, 30%, and 25% in the waveguide14R of the red light (R), the waveguide 14G of green light (G), and thewaveguide 14B of blue light (B), respectively. Thus, the efficiency isvaried depending on the wavelengths of light guided by the waveguides14. In particular, attenuation of the red color is large. This isbecause the spread angle of the red light at a time when the light exitsthe waveguide 14R is larger than those of the green and blue light,since the efficiencies of the colors from the micro lens 52 to theentries of the waveguides 14 are the same.

As described above, as the cell size, that is, the size of thephotoelectric converter 21 becomes smaller, the efficiency of thesolid-state image pickup apparatus 102 is reduced, and the efficiency issignificantly varied depending on the wavelengths.

It should be noted that the light reception efficiencies of thephotoelectric converters 21 with respect to the respective colors arenot different, because the photoelectric converters 21 are made ofsilicon. The silicon has a band gap energy of 1.1 eV to 1.2 eV, whichcorresponds to a wavelength of 1100 nm. That is, even the red lighthaving the longest wavelength of 650 nm falls within the absorption areaof the photoelectric converter 21.

On the other hand, as shown in FIG. 3, in the solid-state image pickupapparatus 1, when an adjustment is made to the efficiency of thewaveguide 14R that guides the red light, the distance Lr of thewaveguide 14R is 580 nm, the distance Lg of the waveguide 14G is 690 nm,and the distance Lb of the waveguide 14B is 840 nm. At this time, theefficiencies become constant at 35%.

As described above, in the solid-state image pickup apparatus 1, evenwhen the pixel size is reduced, the efficiency can be constant as in thesolid-state image pickup apparatus 101 having the large pixel size inthe first comparative example. In other words, the light amounts of thered, green, and blue light guided by the waveguides 14 can be set to beconstant. Further, by adjusting the distances L of the waveguides 14(for example, waveguides 14G and 14B) that guide light having theshorter wavelength to the waveguide 14 (for example, waveguide 14R) thatguides light having the longer wavelength, a design in which thewaveguide 14 penetrates the photoelectric converter 21 is avoided.

Therefore, in the solid-state image pickup apparatus 1, it is possibleto adjust the spectral balance in the differences of the spread anglesfrom the waveguide exit ends 14E of the waveguides 14 due to thewavelengths of light of the colors. Therefore, at a time when signalsthat are output from the photoelectric converters 21 that receive thered, green, and blue light are synthesized and adjusted to obtain animage of a more natural color, a margin is obtained in the imagesynthesis, and a color correction can be easily performed, which canprovide an advantage of obtaining an image excellent in colorreproducing performance.

Further, the solid-state image pickup apparatus 1 has the structure inresponse to the miniaturization. Therefore, for further miniaturization,the distances L from the waveguide exit ends 14E of the waveguides 14 tothe surface of the photoelectric converters 21 are set, thereby makingit possible to respond to the development of a next-generationsolid-state image pickup apparatus. Thus, it is possible to improve thedeveloping speed of the next-generation solid-state image pickupapparatus and reduce the cost for the development thereof, with theresult that the cost reflected to a product can be significantlyreduced.

(Second Example of Structure of Solid-State Image Pickup Apparatus)

A second example of a structure of the solid-state image pickupapparatus according to the first embodiment of the present inventionwill be described with reference to a cross-sectional diagram of aschematic structure of FIG. 8. The second example is different from thefirst example only in the structure of the waveguides, and the othercomponents are the same as those of the first example.

As shown in FIG. 8, on the substrate 11, the pixel array portion 13constituted of the plurality of pixels 12 each including thephotoelectric converter 21 is provided. The photoelectric converter 21converts incident light to an electrical signal. Further on thesubstrate 11, the transfer gate electrode 23 is formed to be adjacent tothe photoelectric converter 21 through the gate insulating film 22.

Further, on the substrate 11, the protection film 41 that covers thephotoelectric converter 21, the transfer gate electrode 23, and the likeis formed. On the protection film 41, the planarization film 42 isformed.

Above the substrate 11, that is, on the planarization film 42, theplurality of wirings 32 are accumulated, and the wiring layer 31including the insulating layer 34 that covers the plurality of wirings32 is formed.

Each of the wirings 32 is made of metal such as copper, tungsten, andaluminum. Around the wiring 32, a barrier metal layer 33 is formed, forexample.

The insulating layer 34 is formed of, for example, a silicon oxide or asilicon-oxide-based material having a low dielectric constant. Thesilicon-oxide-based material has a refractive index of 1.4 to 1.5.

In the wiring layer 31, the waveguides 14 (14B, 14G, and 14R) areformed. The waveguides 14 guide light to the photoelectric converters 21of the plurality of pixels 12. The waveguides 14 may partly be formed inthe planarization film 42. As an example, in the figure, the waveguide14R is partly formed in the planarization film 42.

The waveguides 14 are formed by filling, through a passivation film 37,the waveguide material 36 into waveguide holes 35. The waveguide holes35 are formed in the wiring layer 31 so as to be separated from thewirings 32. Further, the passivation film 37 and the waveguide material36 are also formed on the upper portion of the insulating layer 34 ofthe wiring layer 31. Accordingly, the waveguide material 36 filled inthe waveguide hole 35 serves as the waveguide 14.

In addition, in the waveguide 14, the distances L (Lb, Lg, and Lr)between the waveguide exit ends 14E from which light exits thewaveguides 14 and the surfaces of the photoelectric converters 21 thatreceive light exited are set to be shorter, as the wavelengths of lightbeams that are guided by the waveguides 14 are longer. The waveguideexit ends 14E correspond to each of bottom portions of the waveguideholes 35.

The waveguide material 36 (waveguides 14) is formed of a material havinga refractive index higher than the insulating layer 34, for example, amaterial having a high transmittance of a wavelength in a visible lightarea. Examples of the material include a silicon nitride film, a diamondfilm, a composite material film of diamond and an organic-basedmaterial, a composite material film of titanium oxide and anorganic-based material, and the like.

The waveguide 14 is constituted of the first color (red) pixel waveguide14R, the second color (green) pixel waveguide 14G, and the third color(blue) waveguide 14B. The wavelengths of the first color (red), thesecond color (green), and the third color (blue) become shorter in thestated order. For example, the red color wavelength λr=650 nm, the greencolor wavelength λg=550 nm, and the blue color wavelength λb=450 nm areset.

In addition, above each of the waveguides 14 (light incident side), thecolor filter 51 is formed through the planarization film 44. On thecolor filter 51, the micro lens 52 that guides the incident light to thelight entry of the waveguide 14 is formed.

In this way, the micro lens 52 and the photoelectric converter 21 areoptically connected to each other through the waveguide 14.

Further, the distance L between the waveguide exit end 14E and thesurface of the photoelectric converter 21 that receives light that exitsthe waveguide 14 is set in the same way as the first example.

The distance Lr of the red-color pixel waveguide 14R is set to beshorter than the distance Lg of the green pixel waveguide 14G. Further,the distance Lg of the green pixel waveguide 14G is set to be shorterthan the distance Lb of the blue pixel waveguide 14B.

As an example, the size of the photoelectric converter 21 is set to 1.1μm□, the diameter of the waveguide exit end 14E of the waveguide 14B isset to 460 nm. In this case, for example, when the distance Lr=580 nm isset, Lg=690 nm, and Lb=840 nm are obtained.

It should be noted that in a case where the distances L are less than300 nm, light that exits the waveguide exit ends 14E is almostcompletely received by the photoelectric converters 21 irrespective ofthe wavelengths of light that enters the waveguides 14.

Accordingly, in a case where the distance Lr<300 nm, the distance Lg<300nm, and the distance Lb<300 nm are satisfied, Lr=Lg=Lb can be set.

Of course, when the size of the photoelectric converter 21 is furtherreduced to be less than 1.1 μm□, it is necessary to reduce the distancesL.

In the solid-state image pickup apparatus 2, the same operation andeffect as those in the solid-state image pickup apparatus 1 describedabove can be obtained.

2. Second Embodiment First Example of Method of ManufacturingSolid-State Image Pickup Apparatus

Next, a description will be given on a first example of a method ofmanufacturing a solid-state image pickup apparatus according to a secondembodiment of the present invention with reference tomanufacture-process cross-sectional diagrams of FIGS. 9 to 11.

As shown in FIG. 9A, on the substrate 11, the pixel array portion 13constituted of the plurality of pixels 12 each including thephotoelectric converter 21 that converts the incident light into anelectrical signal is formed. For the substrate 11, a silicon substrateis used as a semiconductor substrate, for example. The photoelectricconverter 21 is formed of a photodiode, for example. Further, on thesubstrate 11, the transfer gate electrode 23 is formed to be adjacent tothe photoelectric converter 21 through the gate insulating film 22. Inaddition, a pixel transistor, a peripheral circuit, and the like (notshown) are also formed.

On the substrate 11, the protection film 41 that covers thephotoelectric converter 21, the transfer gate electrode 23, and the likeis further formed. On the protection film 41 as an insulating film, theplanarization film 42 is formed.

After that, a connection hole (not shown) for electrical connection withthe substrate 11, the transfer gate electrode 23, and the like isformed. A metal material such as tungsten (W), copper (Cu), and aluminum(Al) is filled in the connection hole, thereby forming a plug. The plugis formed by forming the metal material that fills the connection holesover an entire surface of the planarization film 42 and then removing anextra metal material by using a chemical mechanical polishing (CMP)method or the like.

After that, a first insulating layer 34A in which a first wiring layeris formed is formed, and then a wiring groove is formed in the firstwiring layer 34A. Next, a barrier metal layer 33A is formed on an innersurface of the wiring groove. Further, a low-resistive wiring material(e.g., copper (Cu) and aluminum (Al)) that serves as a main wiring thatis embedded in the wiring groove is formed, and then the extra wiringmaterial and barrier metal layer are removed, to form the first wiring32 (32A). For the removal process, a chemical mechanical polishing isused, for example.

In this way, the first wiring layer 31A is formed.

Subsequently, an etching stopper layer 38 (38A) is formed on the firstinsulating layer 34A. The etching stopper layer 38A covers an upperportion of the first wiring 32A. The etching stopper layer 38A serves asa barrier layer for preventing diffusion of copper (Cu) or the like, andis formed of an insulating film such as a silicon nitride (SiN) film anda silicon carbide (SiC) film.

Next, a second insulating layer 34B is formed. The second insulatinglayer 34B is formed of a silicon oxide film or a low-dielectric constantmaterial (silicon oxide carbide (SiOC), methylsilsesquioxane (MSQ),hydro-silsesquioxane (HSQ), or the like) film, for example.

Next, by a dual damascene method or the like, a connection hole (notshown) and a wiring groove are formed in the second insulating layer34B.

Subsequently, a main wiring material is embedded in the wiring grooveand the connection hole through the barrier metal layer 33B. Then, theextra main wiring material and barrier metal layer are removed by thechemical mechanical polishing or the like, thereby forming a secondwiring 32 (32B) in the wiring groove through the barrier metal layer 33Band forming a plug (not shown) in the connection hole through thebarrier metal layer.

In this way, a second wiring layer 31B is formed.

Further, on the second wiring layer 31B, an etching stopper layer 38(38B) is formed as in the case of the formation on the first wiringlayer 31A. The etching stopper layer 38B serves as a barrier layer forpreventing the diffusion of copper (Cu) or the like, and is formed of aninsulating film such as a silicon nitride (SiN) film and a siliconcarbide (SiC) film.

Hereinafter, as in the case of the second wiring layer 31B, a thirdwiring layer 31C, an etching stopper layer (38C), a fourth wiring layer31D, and an etching stopper layer 38 (38D) are formed. Further, aninsulating layer 34E is formed.

In this way, the wiring layer 31 is formed.

Next, as shown in FIG. 9B, on the wiring layer 31, a resist film 61 isformed, and an opening portion 62 is formed (in the light incidentdirection) above the photoelectric converter 21 (21B) that receives thethird color (e.g., blue) light by the lithography technique.

Next, as shown in FIG. 10A, the resist film 61 is used as an etchingmask, and the wiring layer 31 is etched, thereby forming the waveguidehole 35 (35B) up to the surface of the etching stopper layer 38A, forexample. At this time, the distance Lb from the bottom portion of thewaveguide hole 35B to the surface of the photoelectric converter 21(21B) is set to 840 nm. That is, the upper surface of the etchingstopper layer 38A is formed to have the height of 840 nm from thephotoelectric converter 21B.

After that, the resist film 61 is removed. In the figure, a stateimmediately before the removal of the resist film 61 is shown.

Next, as shown in FIG. 10B, on the wiring layer 31, a resist film 63 isformed, and an opening portion 64 is formed (in the light incidentdirection) above the photoelectric converter 21 (21G) that receives thesecond color (e.g., green) light by the lithography technique.

Next, as shown in FIG. 10C, the resist film 63 is used as an etchingmask, and the wiring layer 31 is etched, thereby forming the waveguidehole 35 (35G) up to the surface of the planarization film 42, forexample. Therefore, the planarization film 42 serves as the etchingstopper layer. At this time, the distance Lg from the bottom portion ofthe waveguide hole 35G to the surface of the photoelectric converter 21(21G) is set to 690 nm. That is, the upper surface of the planarizationfilm 42 is formed to have the height of 690 nm from the photoelectricconverter 21G.

After that, the resist film 63 is removed. In the figure, a stateimmediately before the removal of the resist film 63 is shown.

Next, as shown in FIG. 11A, on the wiring layer 31, a resist film 65 isformed, and an opening portion 66 is formed (in the light incidentdirection) above the photoelectric converter 21 (21R) that receives thefirst color (e.g., red) light by the lithography technique.

Next, as shown in FIG. 11B, the resist film 65 is used as an etchingmask, and the wiring layer 31 and the planarization film 42 are etched,thereby forming the waveguide hole 35 (35R) up to the middle of theplanarization film 42, for example. This etching is controlled based onetching time, for example. At this time, the distance Lr from the bottomportion of the waveguide hole 35R to the surface of the photoelectricconverter 21 (21R) is set to 580 nm.

After that, the resist film 65 is removed. In the figure, a stateimmediately before the removal of the resist film 65 is shown.

As a result of the processes described above, as shown in FIG. 11C, thedistances Lr, Lg, and Lb from the bottom portions (waveguide exit endsat the time when the waveguides are formed) of the waveguide holes 35 tothe surfaces of the photoelectric converters 21 are set depending on thewavelengths of light that enters the waveguide holes 35 (35R, 35G, and35G). In other words, because the surfaces of the photoelectricconverters 21 are flush with the substrate 11, and a height H from thesubstrate 11 to the entries of the waveguides 14 is constant, a depth Dof each of the waveguide holes 35 (35R, 35G, and 35B) is set to apredetermined depth (H-L (Lr, Lg, and Lb)).

After that, although not shown, in the case of forming the solid-stateimage pickup apparatus 1, the waveguide material 36 is filled in thewaveguide holes 35 (35R, 35G, and 35B) and formed on the wiring layer31. In this way, the waveguides 14 (14R, 14G, and 14B) made of thewaveguide material 36 is formed in the waveguide holes 35. Further theplanarization film 44 is formed.

Subsequently, on the planarization film 44, at a position correspondingto each of the waveguides 14 (14R, 14G, and 14B), for example, in thelight incident direction of the waveguides 14, the color filter 51corresponding to each color of light guided by the waveguides 14 isformed. Then, the micro lens 52 is formed on the color filter 51. Inthis way, the solid-state image pickup apparatus 1 is formed.

Further, although not shown, in the case of forming the solid-stateimage pickup apparatus 2, the waveguide material 36 is filled in thewaveguide holes 35 (35R, 35G, and 35B) through the passivation film 37and formed on the wiring layer 31. In this way, the waveguides 14 (14R,14G, and 14B) made of the waveguide material 36 is formed in thewaveguide holes 35. Further the planarization film 44 is formed.

Subsequently, on the planarization film 44, at a position correspondingto each of the waveguides 14 (14R, 14G, and 14B), for example, in thelight incident direction of the waveguides 14, the color filter 51corresponding to each color of light guided by the waveguides 14 isformed. Then, the micro lens 52 is formed on the color filter 51. Inthis way, the solid-state image pickup apparatus 2 is formed.

The waveguide material 36 has the refractive index higher than theinsulating layer 34, and is a material having a high transmittance of awavelength in a visible light area, for example. Examples of thematerial include a silicon nitride film, a diamond film, a compositematerial film of diamond and an organic-based material, a compositematerial film of titanium oxide and an organic-based material, and thelike.

Thus, in the method of manufacturing the solid-state image pickupapparatus described above, the spectral balance in the difference of thespread angles from the waveguide exit ends 14E of the waveguides 14 dueto the wavelengths of colors can be adjusted to be constant. As aresult, when signals that are output from the photoelectric converters21 that receive the red, green, and blue light are synthesized andadjusted to obtain an image of a more natural color, a margin isobtained in the image synthesis, and a color correction can be easilyperformed, which can provide an advantage of obtaining an imageexcellent in color reproducing performance.

Further, the solid-state image pickup apparatus has the structure inresponse to the miniaturization. Therefore, for further miniaturization,by using the structure, it is possible to improve the developing speedof the next-generation solid-state image pickup apparatus and reduce thecost for the development thereof, with the result that the costreflected to a product can be significantly reduced.

Second Example of Method of Manufacturing Solid-State Image PickupApparatus

Next, a description will be given on a second example of a method ofmanufacturing a solid-state image pickup apparatus according to thesecond embodiment of the present invention with reference tomanufacture-process cross-sectional diagrams of FIGS. 12 and 13.

As shown in FIG. 12A, on the substrate 11, the pixel array portion 13constituted of the plurality of pixels 12 each including thephotoelectric converter 21 that converts the incident light into anelectrical signal is formed. For the substrate 11, a silicon substrateis used as a semiconductor substrate, for example. The photoelectricconverter 21 is formed of a photodiode, for example. Further, on thesubstrate 11, the transfer gate electrode 23 is formed to be adjacent tothe photoelectric converter 21 through the gate insulating film 22. Inaddition, a pixel transistor, a peripheral circuit, and the like (notshown) are also formed.

On the substrate 11, the protection film 41 that covers thephotoelectric converter 21, the transfer gate electrode 23, and the likeis further formed. On the protection film 41 as an insulating film, theplanarization film 42 is formed.

After that, a connection hole (not shown) for electrical connection withthe substrate 11, the transfer gate electrode 23, and the like areformed. A metal material such as tungsten (W), copper (Cu), and aluminum(Al) is filled in the connection hole, thereby forming a plug. The plugis formed by forming the metal material that fills the connection holesover an entire surface of the planarization film 42 and then removing anextra metal material by using a chemical mechanical polishing (CMP)method or the like. At this time, the height from the surface of thephotoelectric converter 21 to the surface of planarization film 42 isset to be equal to the distance from the waveguide exit end of thewaveguide for guiding the green light to the surface of thephotoelectric converter 21. For example, in the case where thephotoelectric converter 21 is the 1.1 μm□ cell, the height is set to 690nm.

After that, the first insulating layer (34) 34A in which the firstwiring layer is formed is formed, and then the wiring groove is formedin the first wiring layer 34A. At the same time, a dummy pattern groovethat serves as an etching stopper layer used for forming the waveguidehole for the green light is formed.

Next, the barrier metal layer 33A is formed on the inner surface of thewiring groove and the dummy pattern groove. Further, a low-resistivewiring material (e.g., copper (Cu) and aluminum (Al)) embedded in thewiring groove and the dummy pattern groove is formed, and then the extrawiring material and barrier metal layer are removed, to form the firstwiring 32 (32A) and a dummy pattern 71. For the removal process, achemical mechanical polishing is used, for example.

In this way, the first wiring layer 31A is formed.

Subsequently, a diffusion prevention layer 39 (39A) that covers theupper portion of the first wiring 32A is formed on the first insulatinglayer 34A. The height from the surface of the photoelectric converter 21to the surface of the diffusion prevention layer 39A is set to be equalto the distance between the waveguide exit end of the waveguide thatguides the blue light and the surface of the photoelectric converter 21.For example, in the case where the photoelectric converter 21 is the 1.1μm□ cell, the height is set to 840 nm. The diffusion prevention layer39A serves as the barrier layer for preventing the diffusion of copper(Cu) or the like, and is formed of the insulating film such as a siliconnitride (SiN) film and a silicon carbide (SiC) film.

Next, the second insulating layer 34B is formed. The second insulatinglayer 34B is formed of a silicon oxide film or a low-dielectric constantmaterial (silicon oxide carbide (SiOC), methylsilsesquioxane (MSQ),hydro-silsesquioxane (HSQ), or the like) film, for example.

Next, by a dual damascene method or the like, the connection hole (notshown) and the wiring groove are formed in the second insulating layer34B. At the same time, a dummy pattern groove that serves as an etchingstopper layer used for forming the waveguide hole for the blue light isformed.

Subsequently, the main wiring material is embedded in the connectionhole, the wiring groove, and the dummy pattern groove through thebarrier metal layer 33B. Then, the extra main wiring material andbarrier metal layer are removed by the chemical mechanical polishing orthe like, thereby forming the second wiring 32 (32B) in the wiringgroove through the barrier metal layer 33B and forming the plug (notshown) in the connection hole through the barrier metal layer. At thesame time, a dummy pattern 72 is formed in the dummy pattern groove.

In this way, the second wiring layer 31B is formed.

Further, on the second wiring layer 31B, a diffusion prevention layer39B is formed as in the case of the formation on the first wiring layer31A. The diffusion prevention layer 39B serves as the barrier layer forpreventing the diffusion of copper (Cu) or the like, and is formed of aninsulating film such as a silicon nitride (SiN) film and a siliconcarbide (SiC) film.

Hereinafter, as in the case of the second wiring layer 31B, the thirdwiring layer 31C, a diffusion prevention layer 39 (39C), the fourthwiring layer 31D, and a diffusion prevention layer 39 (39D) are formed.Further, the insulating layer 34E is formed.

In this way, the wiring layer 31 is formed.

Next, as shown in FIG. 12B, on the wiring layer 31, a resist film 67 isformed, and an opening portion 68 is formed (in the light incidentdirection) above the photoelectric converter 21 (21B) that receives thethird color (e.g., blue) light by the lithography technique. At the sametime, in the resist film 67, an opening portion 69 is formed (in thelight incident direction) above the photoelectric converter 21 (21G)that receives the second color (e.g., green) light, and an openingportion 70 is formed (in the light incident direction) above thephotoelectric converter 21 (21R) that receives the first color (e.g.,red) light.

Next, as shown in FIG. 13A, the resist film 67 is used as an etchingmask, and the wiring layer 31 is etched. At this time, the etching forforming the waveguide hole 35 (35B) is stopped up to the dummy pattern71. Further, the etching for forming the waveguide hole 35 (35G) isstopped up to the dummy pattern 72. The etching for forming thewaveguide hole 35 (35R) is stopped by time control so that the distanceLr from the bottom portion of the waveguide hole 35R to the surface ofthe photoelectric converter 21 (21R) is 840 nm, for example.

The etching is performed by dry etching or the like. For example, forthe etching of a silicon-based insulating material of the wiring layer31, a carbon fluoride (CF)-based gas or a fluorohydrocarbon (CHF)-basedgas is used, and a compound with silicon having high volatility isformed, thereby performing the etching. Examples of the silicon-basedinsulating material include a silicon oxide film, a silicon-basedlow-dielectric constant film (such as SiOC and SiC), and a siliconnitride film. On the other hand, the metal material such as the dummypatterns 71 and 72 is hardly etched by plasma of the CF-based orCHF-based gas. Therefore, the dummy patterns 71 and 72 each function asthe etching stopper.

After that, as shown in FIG. 13B, the resist film 67 (see, FIG. 13A) onthe wiring layer 31 is removed.

Then, as shown in FIG. 13C, the dummy patterns 71 and 72 (see, FIG. 13C)are removed by an etching.

For the removal of the dummy patterns 71 and 72 each made of the metalmaterial, a wet etching that allows a selective etching of a metalmaterial is used, for example. For example, a case where the dummypatterns 71 and 72 are made of copper (Cu) will be describedhereinafter.

Generally, a material that forms a metal wiring is copper (Cu) of abarrier metal and a main wiring. Copper is relatively easily dissolvedby the acid. Further, when copper is mixed with hydrogen peroxide water(H₂O₂), oxidization of copper is promoted, and the oxidized copper israpidly etched by the acid. For example, in a case of a mixed solutionof a hydrofluoric acid and hydrogen peroxide water, a selection ratio ofcopper to the silicon oxide film of 100:1 or more is obtained. That is,copper can be etched without giving almost any influence on the materialthat forms the insulating layer.

For the barrier metal layer 33 (see, FIG. 12A), tantalum (Ta)-basedmaterial (Ta or TaN) is generally used. The tantalum-based material ishardly etched by a chemical solution that is generally used in asemiconductor process. Therefore, a method of removing the barrier metallayer 33 by a dry etching with an SF₆-based gas is used as an example.But, even if the barrier metal layer 33 has a thickness of 10 nm or lessand is left in the vicinity of the bottom portion of the waveguide holes35, there is no problem in guiding of light. That is, even if thebarrier metal is left as it is, the waveguides satisfactorily function.Further, titanium (Ti) can also be used for the barrier metal. Titaniumis explosively etched with the mixture solution of the hydrofluoric acidand the hydrogen peroxide water as in the case of copper.

In this way, the distances Lr, Lg, and Lb from the bottom portions(waveguide exit ends at the time when the waveguides are formed) of thewaveguide holes 35 to the surfaces of the photoelectric converters 21are set depending on the wavelengths of light that enters the waveguideholes 35 (35R, 35G, and 35G). In other words, because the surfaces ofthe photoelectric converters 21 are flush with the substrate 11, and theheight H from the substrate 11 to the entries of the waveguide holes 35is constant, the depth D of each of the waveguide holes 35 (35R, 35G,and 35B) is set to the predetermined depth (H-L (Lr, Lg, and Lb)).

After that, although not shown, the same processes as those in the firstexample only have to be performed.

The waveguide material 36 has the refractive index higher than theinsulating layer 34, and is a material having a high transmittance of awavelength in a visible light area, for example. Examples of thematerial include a silicon nitride film, a diamond film, a compositematerial film of diamond and an organic-based material, a compositematerial film of titanium oxide and an organic-based material, and thelike.

Thus, in the method (second example) of manufacturing the solid-stateimage pickup apparatus described above, the spectral balance in thedifference of the spread angles from the waveguide exit ends 14E of thewaveguides 14 due to the wavelengths of colors can be adjusted to beconstant. As a result, when signals that are output from thephotoelectric converters 21 that receive the red, green, and blue lightare synthesized and adjusted to obtain an image of a more natural color,a margin is obtained in the image synthesis, and a color correction canbe easily performed, which can provide an advantage of obtaining animage excellent in color reproducing performance.

Further, the solid-state image pickup apparatus has the structure inresponse to the miniaturization. Therefore, for further miniaturization,by using the structure, it is possible to improve the developing speedof the next-generation solid-state image pickup apparatus and reduce thecost for the development thereof, with the result that the costreflected to a product can be significantly reduced.

Third Example of Method of Manufacturing Solid-State Image PickupApparatus

Next, a description will be given on a third example of a method ofmanufacturing a solid-state image pickup apparatus according to thesecond embodiment of the present invention with reference tomanufacture-process cross-sectional diagrams of FIGS. 14 and 15. Thethird example is different from the second example only in that thediffusion prevention film 39 used in the second example is not formed,and a cobalt tungsten phosphorus (CoWP) layer or a copper-manganesealloy layer is formed as a barrier layer on the upper surface of each ofthe wirings 32, for example.

As shown in FIG. 14A, on the substrate 11, the pixel array portion 13constituted of the plurality of pixels 12 each including thephotoelectric converter 21 that converts the incident light into anelectrical signal is formed as in the second example described above.Further, on the substrate 11, the transfer gate electrode 23 is formedto be adjacent to the photoelectric converter 21 through the gateinsulating film 22. In addition, the pixel transistor, the peripheralcircuit, and the like (not shown) are also formed.

On the substrate 11, the protection film 41 that covers thephotoelectric converter 21, the transfer gate electrode 23, and the likeis further formed. On the protection film 41 as an insulating film, theplanarization film 42 is formed.

After that, a connection hole (not shown) for electrical connection withthe substrate 11, the transfer gate electrode 23, and the like isformed. A metal material such as tungsten (W), copper (Cu), and aluminum(Al) is filled in the connection hole, thereby forming a plug.

The height from the surface of the photoelectric converter 21 to thesurface of planarization film 42 after the plug is formed is set to beequal to the distance from the waveguide exit end of the waveguide,which guides the green light, to the surface of the photoelectricconverter 21. For example, in the case where the photoelectric converter21 is the 1.1 μm□ cell, the height is set to 690 nm.

After that, the first insulating layer (34) 34A in which the firstwiring layer is formed is formed, and then the wiring groove is formedin the first wiring layer 34A. At the same time, the dummy patterngroove that serves as an etching stopper layer in forming the waveguidehole for the green light is formed.

The height from the surface of the photoelectric converter 21 to thesurface of first insulating film 34A is set to be equal to the distancefrom the waveguide exit end of the waveguide, which guides the bluelight, to the surface of the photoelectric converter 21. For example, inthe case where the photoelectric converter 21 is the 1.1 μm□ cell, theheight is set to 840 nm.

Next, the barrier metal layer 33A is formed on the inner surface of thewiring groove and the dummy pattern groove. Further, the low-resistivewiring material (e.g., copper (Cu)) embedded in the wiring groove andthe dummy pattern groove is formed, and then the extra wiring materialand barrier metal layer are removed, to form the first wiring 32 (32A)and the dummy pattern 71. For the removal process, a chemical mechanicalpolishing is used, for example.

After that, for example, a cobalt tungsten phosphorus (CoWP) layer or acopper-manganese alloy layer is formed as a barrier layer 73 on thefirst wiring 32 (32A) and the dummy pattern 71.

In this way, the first wiring layer 31A is formed.

Next, the second insulating layer 34B is formed. The second insulatinglayer 34B is formed of a silicon oxide film or a low-dielectric constantmaterial (silicon oxide carbide (SiOC), methylsilsesquioxane (MSQ),hydro-silsesquioxane (HSQ), or the like) film, for example.

Next, by a dual damascene method or the like, the connection hole (notshown) and the wiring groove are formed in the second insulating layer34B. At the same time, the dummy pattern groove that serves as theetching stopper layer used for forming the waveguide hole for the bluelight is formed.

Subsequently, the main wiring material is embedded in the connectionhole, the wiring groove, and the dummy pattern groove through thebarrier metal layer 33B. Then, the extra main wiring material andbarrier metal layer are removed by the chemical mechanical polishing orthe like, thereby forming the second wiring 32 (32B) in the wiringgroove through the barrier metal layer 33B and forming the plug (notshown) in the connection hole through the barrier metal layer. At thesame time, the dummy pattern 72 is formed in the dummy pattern groove.

After that, on the second wiring 32 (32B) and the dummy pattern 72, acobalt tungsten phosphorus (CoWP) layer or a copper-manganese alloylayer is formed as a barrier layer 74.

In this way, the second wiring layer 31B is formed.

Hereinafter, as in the case of the second wiring layer 31B, the thirdwiring layer 31C and the fourth wiring layer 31D are formed. Further,the insulating layer 34E is formed.

In this way, the wiring layer 31 is formed.

Next, as shown in FIG. 14B, on the wiring layer 31, the resist film 67is formed, and the opening portion 68 is formed (in the light incidentdirection) above the photoelectric converter 21 (21B) that receives thethird color (e.g., blue) light by the lithography technique. At the sametime, in the resist film 67, the opening portion 69 is formed (in thelight incident direction) above the photoelectric converter 21 (21G)that receives the second color (e.g., green) light, and the openingportion 70 is formed (in the light incident direction) above thephotoelectric converter 21 (21R) that receives the first color (e.g.,red) light.

Next, as shown in FIG. 15A, the resist film 67 is used as an etchingmask, and the wiring layer 31 is etched. At this time, the etching forforming the waveguide hole 35 (35B) is stopped up to the barrier layer73 of the dummy pattern 71. Further, the etching for forming thewaveguide hole 35 (35G) is stopped up to the barrier layer 74 of thedummy pattern 72. The etching for forming the waveguide hole (35R) isstopped by time control so that the distance Lr from the bottom portionof the waveguide hole 35R to the surface of the photoelectric converter21 (21R) is 840 nm, for example.

After that, as shown in FIG. 15B, the resist film 67 (see, FIG. 15A) onthe wiring layer 31 is removed.

Then, as shown in FIG. 15C, the dummy patterns 71 and 72 and barrierlayers 73 and 74 (see, FIG. 15A) are removed by an etching.

For the removal of the dummy patterns 71 and 72 each made of the metalmaterial, a wet etching that allows a selective etching of a metalmaterial is used, for example.

In this way, the distances Lr, Lg, and Lb from the bottom portions(waveguide exit ends at the time when the waveguides are formed) of thewaveguide holes 35 to the surfaces of the photoelectric converters 21are set depending on the wavelengths of light that enters the waveguideholes 35 (35R, 35G, and 35G). In other words, because the surfaces ofthe photoelectric converters 21 are flush with the substrate 11, and theheight H from the substrate 11 to the entries of the waveguide holes 35is constant, the depth D of each of the waveguide holes 35 (35R, 35G,and 35B) is set to the predetermined depth (H-L (Lr, Lg, and Lb)).

After that, although not shown, the same processes as those in the firstexample only have to be performed.

Here, a description will be given on a method of forming the barrierlayer 73 formed on the upper surfaces of the wirings 32 and the uppersurface of the dummy patterns 71 and 72.

The upper surfaces of the wirings 32 and the dummy patterns 71 and 72are the copper wirings.

For the formation of a selective barrier metal on the upper portion ofthe copper wiring, cobalt tungsten phosphorus (CoWP), cobalt tungstenboron (CoWB), or the like by electroless plating is used.

A process of forming the selective barrier metal is introduced after thechemical mechanical polishing of the extra barrier metal and copper toform the copper wiring. The process is significantly easy. A catalystsuch as palladium (Pd) is given (this process may be omitted), andthereafter the electroless plating is just performed. The electrolessplating is formed by giving or taking electrons. Therefore, a growth canbe obtained not on the insulating material such as the silicon oxidefilm but on the metal portion such as copper. Accordingly, a selectivegrowth only on the upper portion of the copper wiring can be obtained. Abarrier metal formed of CoWP, CoWB, or the like inherently has an effectof diffusion prevention of copper or the like, and thus the siliconnitride (SiN) film, the silicon carbide (SiC) film, or the like is notrequired unlike the first and second examples described above.

As a result, in the method of manufacturing the solid-state image pickupapparatus described above, the spectral balance in the difference of thespread angles from the waveguide exit ends 14E of the waveguides 14 dueto the wavelengths of colors can be adjusted to be constant. As aresult, when signals that are output from the photoelectric converters21 that receive the red, green, and blue light are synthesized andadjusted to obtain an image of a more natural color, a margin isobtained in the image synthesis, and a color correction can be easilyperformed, which can provide an advantage of obtaining an imageexcellent in color reproducing performance.

Further, the solid-state image pickup apparatus has the structure inresponse to the miniaturization. Therefore, for further miniaturization,by using the structure, it is possible to improve the developing speedof the next-generation solid-state image pickup apparatus and reduce thecost for the development thereof, with the result that the costreflected to a product can be significantly reduced.

Furthermore, the third example provides two significant advantages.

First, SiN and SiC having a relatively large refractive index are notused. Therefore, light that enters the waveguide is prevented fromleaking, which increases the amount of light that reaches thephotodiode. As a result, the sensitivity can be increased.

Second, the function of the etching stopper is advantageous. The surfaceof the etching stopper of the second example is formed of copper (Cu),which relatively easily corrodes away. In contrast, the cobalt-basedmaterial is relatively unlikely to corrode. Thus, a margin can beobtained during exposure with plasma.

3. Third Embodiment Example of Structure of Image Pickup Apparatus

A description will be given on an example of a structure of an imagepickup apparatus according to a third embodiment of the presentinvention with reference to a block diagram of FIG. 16. In the imagepickup apparatus, the solid-state image pickup apparatus according tothe embodiments of the present invention is used.

As shown in FIG. 16, an image pickup apparatus 200 includes asolid-state image pickup apparatus (not shown) in an image pickupportion 201. On a light-collecting side of the image pickup portion 201,a light-collecting optical portion 202 that forms an image is provided.Further, to the image pickup portion 201, connected is a signalprocessing portion 203 having a drive circuit that drives the imagepickup portion 201 and a signal processing circuit that performs animage processing on a signal that has been subjected to thephotoelectric conversion in the solid-state image pickup apparatus. Inaddition, an image signal that has been subjected to the processing inthe signal processing portion 203 can be stored in an image storageportion (not shown). In the image pickup apparatus 200, the solid-stateimage pickup apparatus 1 or 2 described in the above embodiments can beused for the solid-state image pickup apparatus.

The image pickup apparatus 200 of the present invention uses thesolid-state image pickup apparatus 1 or 2 according to the embodimentsof the present invention, so the spectral balance in the solid-stateimage pickup apparatuses 1 and 2 can be adjusted. Therefore, an imagesynthesis margin can be obtained in making an adjustment for an image ofa more natural color, and a color correction can be easily performed,with the result that the advantage of obtaining an image excellent incolor reproducing performance can be provided.

In addition, the image pickup apparatus 200 may have a one-chip form ora module-like form in which an image pickup function in which the imagepickup portion and the signal processing portion or the optical systemare collectively packaged is implemented. In addition, the solid-stateimage pickup apparatuses 1 and 2 according to the present invention canalso be applied to an image pickup apparatus as described above. Here,the image pickup apparatus refers to a mobile apparatus having a camera,an image pickup function, or the like. Further, the meaning of “pickingup an image” broadly includes fingerprint detection, in addition topicking up an image at a time of general shooting with a camera.

It should be understood by those skilled in the art that variousmodifications, combinations, sub-combinations and alterations may occurdepending on design requirements and other factors insofar as they arewithin the scope of the appended claims or the equivalents thereof.

What is claimed is:
 1. A method of manufacturing a solid-state imagepickup apparatus, comprising: forming, on a substrate, a pixel arrayportion constituted of a plurality of pixels each having a photoelectricconverter that converts incident light to an electrical signal; forming,above the substrate, a wiring layer including multilayer wirings and aninsulating layer that covers the wirings; and forming, in the wiringlayer, a waveguide that guides light to the photoelectric converter ofeach of the plurality of pixels, wherein the waveguide is formed to havea waveguide exit end from which light exits the waveguide so that adistance between the waveguide exit end and a surface of thephotoelectric converter that receives light from the waveguide becomeshorter, as wavelengths of light guided by the waveguide are longer. 2.The method of manufacturing a solid-state image pickup apparatusaccording to claim 1, further comprising: forming, in a state whereetching stopper layers are formed in the insulating layer so that asurface of each of the etching stopper layers is set at a position thatdefines a height from the surface of the photoelectric converter to abottom surface of the waveguide, a waveguide hole by etching theinsulating layer up to a predetermined one of the etching stopperlayers; and forming a waveguide by filling a waveguide material in thewaveguide hole.
 3. The method of manufacturing a solid-state imagepickup apparatus according to claim 1, further comprising: forming, in astate where etching stopper layers are formed in the insulating layer sothat a back surface of each of the etching stopper layers is set at aposition that defines a height from the surface of the photoelectricconverter to a bottom surface of the waveguide, a waveguide hole byetching the insulating layer up to a predetermined one of the etchingstopper layers and etching the etching stopper layer; and forming awaveguide by filling a waveguide material in the waveguide hole.
 4. Themethod of manufacturing a solid-state image pickup apparatus accordingto claim 3, wherein the etching stopper layers are each formed of adummy pattern formed of the same layer as the wiring formed in thewiring layer.
 5. The method of manufacturing a solid-state image pickupapparatus according to claim 4, wherein the dummy pattern has a surfaceon which a barrier layer is formed.